Electric circuit breaker



'May 5, 1942. H. THOMMEN 2,282,268

ELECTRIC CIRCUIT BREAKER Filed Feb. 8, 1940 Patented May 5, 1942ELECTRIC CIRCUIT BREAKER Hans Thommen, Baden, Switzerland, assignor toAktiengesellschaft Baden, Switzerland Application Brown,

Boveri & pie

February a, 1940, Serial No. 317,946

In Germany May 6, 1938 4 Claims.

This invention relates to electrical circuit breakers and particularlyto heavy duty switching systems including a circuit breaker and adisconnect switch that are operated, in proper sequence, by air underpressure and in which an air blast passes over or between the circuitbreaker contacts to extinguish the arc.

Protective switching systems of this type for use on lines carryingheavy currents have previously required contacts of large dimensions'atboth the circuit breaker and the disconnect switch, and the switcheswere of relatively heavy constructions. It has been proposed to bridge acurrent-carrying switch across the circuit breaker and disconnect switchto carry the normal load current. This arrangement is open to theobjection that it materially increases the time required for an openingof the switch system;-it being necessary to open the current-carryingswitch, then the circuit breaker, and finally the disconnect switch. Theprior switch systems were thus characterized by a relatively longoperating time when a third switch was bridged across the circuitbreaker and disconnect switch or by circuit breaker contacts in whichthe number and size of the multiple section contacts for carrying thehigh load current interfered with the air blast that was to extinguishthe arc.

An object for the present invention is to provide an electric circuitbreaker having contacts of such design that the entire rated current maybe carried by the circuit breaker, an air cylinder and piston forholding the contacts in engagement under such pressure that the loadcurrent is carried without undue heating, and valve mechanism forsupplying air under pressure to the other end of the cylinder to openthe contacts. An object is to provide a circuit breaker of the typestated in which the contacts take the form of a fixed annular or nozzlecontact and a movable blade or plunger contact which seats upon thenozzle contact when the circuit breaker is closed, the contacts beinglocated in a chamber that is normally under atmospheric pressure and incommunication with that end of the cylinder to which pressure air issupplied to open the circuit breaker, and the valve mechanism includes avalve operable upon the introduction of pressure air into the chamber tovent the opposite end of the cylinder to atmosphere.

These and other objects and advantages of the invention will be apparentfrom the following specification when taken with the accompanyingdrawing in which the single figure is an elevation, with parts insection, of a circuit breaker embodying the invention.

The grounded supporting frame I of the circuit breaker system carries atanki2 in which compressed air is stored, a main blow or control valve 3for controlling the flow of the pressure air to the operating mechanism,and hollow insulators 4, 5 that support the circuit breaker. The blowvalve is actuated in the usual manner, for example by a piston 3a towhich pressure air is admitted by a pilot valve 3b. The casting or bodymember 6 which is carried by the insulator 5 has an air passage 1 thatextends from the hollow insulator 4 to the upper surface of the casting.An air chamber is formed above the casting 6 by an insulating cylinder 8that carries a hollow casting 9 that constitutes one terminal of thecircuit breaker. A contact ID on the terminal casting 9 has the form of'a nozzle which presents a round surface for engagement by the domedcontact I I on the upper end of the switch blade or plunger I2.

The plunger I2 extends through the body member 6 and has a flange orpiston I3 that slides in a cylinder I4 in the lower portion of themember 6. A port I5 connectsthe upper end of the cylinder I4 to the airpassage 1, and a vent at the lower end of the cylinder is controlled bya valve I6 that is slidable in the member 6 and carries a piston I! thatis normally held in raised or vent-closing position by a spring I8. Thevalve l6 and piston I1 are both acted upon by the pressure within thelower end of the cylinder, and the valve assembly is therefore balancedor approximately balanced against this pressure but not against pressureexerted on the upper face of piston I1.

The lower end of the cylinder is closed by a casting l9 that is carriedby the insulator 5, and a passage 20 extends through the casting I9 tosupply pressure air to the lower face of the piston I3. A measuringorifice or throttle member 2| is inserted in the passage 20 to limit theflow of air when the vent valve I6 is open.

The lower end of the circuit breaker blade 12 has leaf contacts 22 forengagement by the disconnect switch blade 23 that is pivotally supportedon the insulator 24 and moved to open position by link 25 and a pressurecylinder 25' after the circuit breaker is opened. A strap 26 oninsulator 24 serves as the second terminal for the switch assembly.

The parts are illustrated in their normal closed positions and thecircuit extends from terminal strap 26 and the disconnect switch 23, 22,through the circuit breaker blade l2, contacts I! and ii. to the otherterminal 0. The upper end of the cylinder is at low or atmosphericpressure and the contacts II, II are held in engagement by pressure airthat enters the lower end of the cylinder I through the passage Ill andhollow insulator I. The rounded surfaces of the contacts restrict thecontacting area to approximately a line and the high pressure engagementaffords a low resistance contact capable of carrying heavy currentswithout undue heating.

The main valve 3 is actuated to admit high pressure air to passage 1when the circuit breaker is to be opened. The high pressure air passesto the upper end of the cylinder it through the port II and also acts onthe small piston I! to open the vent valve It. The piston I8 is forceddownwardly to separate contact II from the fixed contact II, and the arcis extinguished by the blast of air that passes over the tip of contactH to escape through the nozzle contact Ill. The throttle member 2|restricts the fiow of air to the lower face of piston l3 and a rapidopening of the circuit breaker is obtained whether or not a valve isemployed to close the passage 20. The disconnect switch 23 is preferablyopened automatically in timed relation to the opening of the circuitbreaker but the mechanisms for this operation are not-shown as they formno part of the present invention.

The disconnect switch is of course closed again before valve 3 isadjusted to vent the pressure air from the upper end of the cylinder andthe chamber which encloses the contacts. As illustrated, the mechanismfor operating the disconnect switch may comprise pipes 21, 28 foradmitting pressure air to the opposite ends of the cylinder 25; the pipe21 leading to the low pressure side of the blow valve 8 and the fiowthrough pipe 2! being controlled by a valve 20.

It is to be understood that the described construction is illustrativeof the invention and that various changes may be made in the parts,their sizes, shapes and relative arrangements without departure from thespirit of my invention as set forth in the following claims.

I claim:

1. A circuit breaker comprising means defining an arc-extinguishingchamber, a nozzle contact carried by one wall of the chamber, a slidingmember having a domed contact for seating against said nozzle contact, acylinder and piston supporting said sliding member for movement axiallyof the chamber, means for continuously admitting air to one end of thecylinder to displace said piston to hold said domed contact in firmengagement with said nozzle contact, a port connecting the other end ofthe cylinder to said chamber, means responsive to pressure within saidchamber to vent the first end of the cylinder, and valve means foradmitting pressure air to said chamber.

2. A circuit breaker as claimedin claim 1,

wherein said venting means comprises a second piston slidable in a wallof said chamber, and a vent valve carried by said second piston, thepressure within the chamber being exerted on the outer face of thesecond piston and the pressure within the first end of the cylinderbeing applied in opposite directions to said second piston and valve.

3. A circuit breaker comprising areciprocating blade member, a pistoncarrying said member and movable in a cylinder, a tank for storing airunder pressure, a contact on one end of the blade member, a fixedcontact in line with said blade member contact, a permanently open airvpassage connecting said tank to the end of said cylinder opposite saidcontacts, means in said passage restricting the-flow of airtherethrough, valve means and a second passage for supplying pressureair from the tank to the other end of the cylinder, andpressure-responsive vent means operable by pressure air admitted to saidother end of the cylinder to vent to atmosphere the first end of thecylinder.

4. A circuit breaker adapted to cary heavy currents comprising a bodystructure including a cylinder, a sliding member extending throughoperable by pressure air in the chamber for vent-

